All of our heat is generated from chemical reactions when your body
converts sugars to energy. If this is the case why do reptiles need to
get heat from the sun as I'm sure they have to convert sugars to energy
as well? And what in our body regulates that temperature so that it
remains steady and then even elevates during times of infection?
Most energy comes from the oxidation of glucose (glycolysis). We control this process strictly, so we can stabilize our body temperature. If we exercise, we burn extra glucose, creating more heat. We compensate by i.e. sweating. If we sleep, we use less glucose, so our body temperature drops. Hence the nice and warm blankets.
Ectothermic animals can't control glycolysis because they lose more heat than they produce. They need an external heat source to keep the glycolysis going to produce ATP to fuel processes like muscle action and signal conduction.
Most energy comes from the oxidation of glucose (glycolysis). We control this process strictly, so we can stabilize our body temperature. If we exercise, we burn extra glucose, creating more heat. We compensate by i.e. sweating. If we sleep, we use less glucose, so our body temperature drops. Hence the nice and warm blankets.
Ectothermic animals can't control glycolysis because they lose more heat than they produce. They need an external heat source to keep the glycolysis going to produce ATP to fuel processes like muscle action and signal conduction.
That would be reasonable, if we would not have ways to regulate body temperature.
I could find (quick search, though) any literature on physical activity vs. core temperature. However, in extreme cases of 'not eating a lot', e.g. anorexia, the core temperature is significantly lower than in healthy subjects (Source). However, the other extreme does not fly: obese patients have no higher body temperature than non-obese patients (Source). I think the body has a great way to regulate temperature, and only in extreme cases (i.e. a lack of available glucose), the body can't compensate. The extra energy that is freed while exercising is lost through sweating and other mechanisms.
A physically active and fit person would have a quicker metabolism, as well as more efficient heart, meaning not only that your heart has to beat less but that it travels through the body faster, generating more heat. The surface area is certainly part of it as well, as the blood has more area to cover to heat up all parts of the body.
How the body uses blood flow for temperature regulation. By constricting blood vessels in the appendages, core body heat can be conserved. This keeps our vital organs warmer in cases of hypothermia. The opposite can be true in a warm environment where blood flow can increase through our appendages. This allows heat to dissipate from a the greater surface area present in our appendages.
The hypothalamus is called the body's thermostat and regulates temperature.
You could spare yourself the effort and Google a bit. Googling 'body thermostat' gives you quite some interesting links.
I could find (quick search, though) any literature on physical activity vs. core temperature. However, in extreme cases of 'not eating a lot', e.g. anorexia, the core temperature is significantly lower than in healthy subjects (Source). However, the other extreme does not fly: obese patients have no higher body temperature than non-obese patients (Source). I think the body has a great way to regulate temperature, and only in extreme cases (i.e. a lack of available glucose), the body can't compensate. The extra energy that is freed while exercising is lost through sweating and other mechanisms.
A physically active and fit person would have a quicker metabolism, as well as more efficient heart, meaning not only that your heart has to beat less but that it travels through the body faster, generating more heat. The surface area is certainly part of it as well, as the blood has more area to cover to heat up all parts of the body.
How the body uses blood flow for temperature regulation. By constricting blood vessels in the appendages, core body heat can be conserved. This keeps our vital organs warmer in cases of hypothermia. The opposite can be true in a warm environment where blood flow can increase through our appendages. This allows heat to dissipate from a the greater surface area present in our appendages.
The hypothalamus is called the body's thermostat and regulates temperature.
You could spare yourself the effort and Google a bit. Googling 'body thermostat' gives you quite some interesting links.
While
glycolysis is an important part of thermoregulation, there are several
differences between endothermic and ectothermic organisms which allow
for more efficient thermoregulation. Endothermic organisms have a higher
mitochondrial concentration
in their tissues, which allows more metabolic heat than ectotherms. The
mitochondria of endothermic organisms are also different than those of
ectotherms. Their uncoupled
oxidative phosphorilation enables them to produce more heat than
ectotherms as well.
When you mention elevated tempreratures during times of infection, you are describing a fever. Fevers are initiated when a pyrogen like Interleukin-1 (IL-1), which is produced by lymphocytes when they encounter pathogens like bacteria, binds to a receptor on the hypothalamus, which is in control of our body temperature.
Mitochondria in brown fat tissue generate heat. As you may already be aware, Mitochondria oxidize substances to form a proton gradient, and then use the hydrogen diffusing across the inner membrane to power ATP-synthase which produces ATP. What mitochondria can also do, however, is allow the hydrogen to diffuse through thermogenin, a protein hydrogen channel, into the matrix without producing ATP. Since the hydrogen are crossing the gradient, and aren't using their energy to produce ATP, their energy is instead released as heat. Thermogenin is unique to the brown tissue of mammals, I don't know whether or not cold blooded animals have any type of equivalent.
When you mention elevated tempreratures during times of infection, you are describing a fever. Fevers are initiated when a pyrogen like Interleukin-1 (IL-1), which is produced by lymphocytes when they encounter pathogens like bacteria, binds to a receptor on the hypothalamus, which is in control of our body temperature.
Mitochondria in brown fat tissue generate heat. As you may already be aware, Mitochondria oxidize substances to form a proton gradient, and then use the hydrogen diffusing across the inner membrane to power ATP-synthase which produces ATP. What mitochondria can also do, however, is allow the hydrogen to diffuse through thermogenin, a protein hydrogen channel, into the matrix without producing ATP. Since the hydrogen are crossing the gradient, and aren't using their energy to produce ATP, their energy is instead released as heat. Thermogenin is unique to the brown tissue of mammals, I don't know whether or not cold blooded animals have any type of equivalent.
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